In co-pending application Ser. No. 784,367, filed Apr. 4, 1977 now abandoned and Ser. No. 829,781, filed Sept. 1, 1977, now U.S. Pat. No. 4,123,438, granted Oct. 31, 1978, the present applicants have disclosed a method for making unsubstituted 2-pyrrolidones by reacting the same under hydrogenation conditions and at low pressures in the presence of ammonia. That process has not, however, produced N-substituted 2-pyrrolidones.
However, the manufacture of N-substituted 2-pyrrolidones has been investigated elsewhere in the prior art, and there has been an interest in making such compounds as well, and also in improved processes for doing so.
One possible method for the preparation of those pyrrolidones is described in British Patent Specification No. 1,089,083 involving the use of succinic acid, or an alkylsubstituted succinic acid, as starting materials, and converting the same to the cyclic product by reaction with a primary amine. However, this method required prolonged heating, for instance, from 6 to 11 hours, at temperatures of from 200.degree. to 300.degree. C. and at elevated pressures of at least 50 bars and preferably even above 220 bars. Thus, while said to be "simple to operate", in fact such prior art process is at least somewhat less than desirable. Further, such process produces succinimide by-products which require separation from the pyrrolidone products.